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Old February 9th, 2010, 07:11 PM   #1
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? Uncompressed 8 bit Acquisition / AVCHD

Hi

I am using a BM Intensity Pro Card. Using the BM Media Express v2 acquisition program that comes with the card preferences set to 8 bit uncompressed.

I'm hooking up a little Canon HF 10 that can capture max to memory card 17mbit/sec, hooked up to FCP and using Prores HQ I can capture at 24mbit/sec.

I've just started experimenting with the BM Media Express software and FCP is telling me I'm capturing at 99.1mbit/sec.

If I do the Apple "get Info" it tells me the clip is capturing at the following specs:

Dimension : 1920 x 1080
Codecs : Linear PCM, Component Y'CbCr 8-bit 4:2:2 ordered Cb Y'0 Cr Y'1
Color Profile HD (1-1-1)

Given that AVCHD Codec has a maximum record data rate of 24mbit/sec and 4:2:0 colour space, am I really capturing 4:2:2 colour space?

I'm capturing to a Firmtek 5 Bay 2.3TB Raid 0

I would appreciate anyone's opinion who knows much more about these things than me.

Many Thanks

Michael
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Old February 10th, 2010, 05:05 PM   #2
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Need a bit more clarification

Hi Michael,
Need a bit more info.You do not say whether you are capturing live from the sensor or off the cards. If you are capturing live it is indeed 4:2:2 but if you have it set to uncompressed it would be something in the region of 120 Megabytes a second - not 99 mbits.

If you are re-capturing footage that has been already been encoded to AVCHD, although the uncompressed codec will capture at 4:2:2 your source being 4:2:0 will not add anything of use IMHO. Better to transcode to an edit friendly codec rather than capture in real time of that is the case.

Give me more info and I will try to be more specific
H
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Old February 10th, 2010, 08:16 PM   #3
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Hi Henry

Many thanks for your reply.

The Cam is fed straight into the back of the Intensity Pro via HDMI

When I'm capturing direct to the Raid drive via the BM Media Express program it creates .mov files and a 4min 25sec clip takes up 27.59 GB.

I then open up FCP and import the .mov file directly into the Browser -> Transpose it into the time line.

FCP plays this clip without any problem or need to render.

This is where FCP in the Browser gives me the the info about 99.1mbits/sec

I was quite surprised that the Apple "Get Info" function applied to each .mov file (off the HDD) gave me the info that it was was recording 4:2:2 etc

Given that it is such a tiny little cmos sensor in the cam, I was thinking that maybe there was some considerable interpolation going on.

Or is the cam just supporting the the lens and CMOS sensor and the BM Intensity Pro card is recording in real 4:2:2 ?

Where did you get, or how do you arrive at the 4:2:2 colour space would be or should be capturing at 120mbits/sec ?

Many thanks again

Michal
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Old February 11th, 2010, 05:29 AM   #4
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Hiu Michael,
Well I have been capturing HDMI for over a year now and on all the current Canon camcorders, capturing live is 4:2:2. Check the Blackmagic design site or Convergent design white papers on this.

You are capturing at about 112 MB/sec to get a 27 Gb file in 4 minutes by my math to your RAID. I don't use FC so unsure about the info it is giving.

Blackmagic design actually have a page dedicated to this

Blackmagic Design: Intensity Quality

The sensor size doesn't come into it really.The camera is spitting out uncompressed video which is post in-camera processing but pre compression. It just so happens to have a small sensor but it could have been on large sensor camera.But no such product exists yet within our price range.That is why some of us are waiting for the first VDSLR to spit out truly uncompressed FULL HD HDMI so that we have uncompressed HDMI and also good DOF control.
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Old February 11th, 2010, 03:25 PM   #5
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Hey Henry

Thanks for your reply again.

Yes, I think your on the money. That link goes a long way to explaining it all.

So, maybe it's not about the camera at all, but how fast you can capture HD, as you say, pre-compression.

The Intensity is limited to 8 bit uncompressed. Hhm? Maybe that Matrox card is looking more of an option.

BM Speed Test program says my raid can write at (80% free space) 187 MB/S

In that instance, improving Raid performance and the ability to capture via capture cards puts more focus back on to the glass than all the carry on about which camera brand has the best / optimal proprietary card media.

I re-read the Intensity manual and the 99.1 mb/s maybe correct. I've added a small extract from the manual.

Anyway, thanks for your input, all is much clearer now.

Cheers

Michael
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